Passengers are being advised to contact their airlines before travelling.

NATS said it was restricting flights “in accordance with international civil aviation policy”.

A NATS spokesman was quoted as saying: “The Volcanic Ash Advisory Centre has issued a forecast that the ash cloud from the volcanic eruption in Iceland will track over Europe tonight.

“NATS is working with Eurocontrol and our colleagues in Europe’s other air navigation service providers to take the appropriate action to ensure safety in accordance with international aviation policy.”

Airports operator BAA said: “Following advice from the Met Office the National Air Traffic Service has introduced restrictions to UK airspace this morning as a result of volcanic ash drifting across the United Kingdom from Iceland.

“Passengers intending to fly today are asked to contact their airline for further information and should expect disruption in the coming hours.”